Jane E. Visvader1, Jeffrey M. Rosen2 and Samuel Aparicio3 1The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia 2Baylor College of Medicine, Houston, Texas 77030, USA 3University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada Correspondence: visvaderwehi.edu.au

Breast cancer kills hundreds of thousands of people every year. Rapid progress over the past two decades has increased our understanding of the genetic and environmental risk factors for disease. It has also shed light on drivers of tumor progression and the molecular landscape underpinning tumor heterogeneity, as well as the role of the microenvironment and the immune system. These strides forward should lead to more effective and tailored therapies for early- and late-stage patients.